(a) Field of the Invention
The present invention relates to an organic light emitting diode display and a manufacturing method thereof.
(b) Description of the Related Art
Recent trends toward lightweight and thin personal computers and televisions sets have increased the desire for lightweight and thin display devices associated therewith. Flat panel displays, such as a liquid crystal display (“LCD”) satisfying such requirements, are being substituted for conventional cathode ray tubes (“CRTs”).
However, because the LCD is a passive display device, an additional back-light as a light source is needed. In addition, the LCD has additional drawbacks such as a slow response time and a narrow viewing angle.
Among the flat panel displays, an organic light emitting diode (“OLED”) display has recently been the most promising as a display device for solving these drawbacks associated with other flat panel displays.
The OLED display includes two electrodes and an organic light emitting layer interposed between the two electrodes. One of the two electrodes injects holes and the other electrode injects electrons into the organic light emitting layer. The injected electrons and holes are recombined to form excitons, which emit light as release energy.
Because the OLED display is a self-emissive display device, an additional light source is not necessary such that the OLED display has lower power consumption, as well as a high response speed, wide viewing angle and high contrast ratio.
On the other hand, the OLED display includes a plurality of pixels such as red pixels, blue pixels and green pixels, and images of full colors may be displayed by selectively combining these pixels.
However, the OLED display has different light emitting efficiency according to light emitting materials. That is, a material having low light emitting efficiency among red, green and blue cannot represent the colors of a desired color coordinate, and it is also difficult to display a desired white color due to the material having the low light emitting efficiency in the case of emitting white color by combining red, green and blue.
To improve the light emitting efficiency, a micro-cavity may be used.
In a micro-cavity, light is repeatedly reflected between a reflection layer and a translucent layer in which both layers are separated by a predetermined distance (e.g., an optical path length) such that a strong interference effect is generated in the light. Accordingly, light of a specific wavelength is constructive, and light of remaining wavelengths is destructive.
Accordingly, the luminance and the color reproducibility may be simultaneously improved at the front side.
However, to represent full colors by using the micro-cavity, the red pixel, green pixel and blue pixel must have different optical path lengths corresponding to the wavelengths of each pixel. To form the different optical path lengths for each pixel, additional processing steps are required to form the micro-cavities for each pixel are required, thus increasing the number of total manufacturing processes.